I followed the docs and bootstrapped my environment and all went well. But, for those looking to install MongoDB, the Mongo docs can be a bit lacking and I found this post:
http://arcanebytes.com/2013/09/03/mongodb-installation-on-mac-os-x/ to be far more useful. For the record, too, I'm on a MacOS 10.7.5 and that post is for 10.8. Worked well for me, though.
joe